For those of you having trouble finding these plants in stores (as often happens) I'd like to recommend Prairie Moon Nursery which sells almost 100% native plants. http://www.prairiemoon.com/
Their use of the word Savana instead of partial sun is a little confusing though. They're a great source of plants for where ever you are in the country I think.
Clovers are considered invasive and nonnative to the US. Most clovers anyhow, I'm not sure of any natives off hand. That White Dutch Clover bees like are imported BUT as far as invasive plants go, you could certainly do worse. Go ahead and plant clover. It's a 4 inch tall plant, that is easily shaded out by just about anything else you plant. The issue is when you have huge patches of clover everywhere. They can actually put to much nitrogen into the soil and that effects all your fruit trees, and can limit the plants that grow around there. A lot of native plants absolutely hate fertilizer.
It's hard to recommend a native alternative that is the right size. One plant I'm trying out this year though is Lead Plant, Amorpha canescens. It's native to the central US though. (I'm in from New Jersey but I really wanted to try this one out.) http://www.prairiemoon.com/seeds/trees-shrubs-vines/amorpha-canescens-lead-plant/?cat=0&from_search=Yhttp://plants.usda.gov/java/profile?symbol=AMCA6&mapType=nativity&photoID=amca6_002_avp.tif